Abstract
We report on a complete optogalvanic spectrum of a discharge burning in a La-Ar gas mixture, in the spectral range 5610–6110 Å (17,851 to 16,364 cm−1). About 1900 overlapping laser scans, each between 1 and 1.5 cm−1 wide, were necessary to cover this range. The resolution of the spectra is limited by the Doppler width of the spectral features to about 0.03 cm−1 (or ca. 0.01 Å) and is comparable with a Fourier-transform spectrum, but the sensitivity is much higher. Indeed, we could find more than 1800 lines, from which about 800 could be classified as transitions between known energy levels. The main focus of the investigations was to discover previously unknown energy levels by means of excitation of unclassified spectral features.
Highlights
Lanthanum (La, Z = 57) has the electron ground state configuration [Xe]5d6s2 and an empty4f shell, while for the elements with Z = 58 to 71 this 4f shell is partially filled, but the 6s2 shell is kept
In the spectral range treated in this work (5610–6110 Å), 96 spectral lines belonging to the spectra of La I
In this paper we report on previously unknown energy levels
Summary
In the present investigation the second, long-living radioactive isotope with mass number 138 (0.09%) is not visible in the spectra and neglected. In the spectral range treated in this work (5610–6110 Å), 96 spectral lines belonging to the spectra of La I (neutral atom) or La II (first ion) are listed in those tables. The analysis of the spectra led to the list of energy levels summarized by Martin et al in 1978 [3], where 80 even-parity and 156 odd-parity levels are given. The list of energy levels is by far not complete. Limited by the scan range of the used source of tunable laser light Each between in order to perform systematic investigations.
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